[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 250549
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU AUG 25 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM
THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON
SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0345 UTC.

...SPECIAL FEATURES...
TROPICAL STROM KATRINA IS CENTERED NEAR 26.1N 78.4W...OR ABOUT
35 MILES...30 NM...SSE OF FREEPORT GRAND BAHAMA ISLAND AND ABOUT
110 MILES...95 NM...E OF THE SE COAST OF FLORIDA AT 25/0600 UTC
MOVING W AT 7 KT. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH
GUSTS TO 55 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER HEADERS
MIATCPAT1/WTNT32 KNHC FOR MORE DETAILS. KATRINA CONTINUES TO
BECOME BETTER ORGANIZED TONIGHT WITH CONVECTION FILLING OVER THE
CENTER. SCATTERED MODERATE/STRONG CONVECTION IS WITHIN 60 NM OF
THE CENTER. FEEDER BANDS OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION EXTENDS OUT TO WITHIN 150/175 NM OF THE CENTER
INCLUDING S FLORIDA AND THE CENTRAL BAHAMAS N OF LONG ISLAND.

A 1009 MB LOW IS CENTERED BETWEEN THE CAPE VERDE ISLANDS AND THE
LESSER ANTILLES NEAR 17.5N42.5W...ALONG A TROPICAL WAVE S OF 24N
ALONG 42W/43W MOVING W NEAR 10 KT. THE LOW LEVEL CENTER REMAINS
COMPLETELY EXPOSED DUE TO SOUTHWESTERLY SHEAR AS A RESULT OF A
MID LEVEL INVERTED TROUGH EXTENDING FROM 15N43W TO 21N42W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 17N-21N
BETWEEN 37W-42W. ALTHOUGH IS SYSTEM REMAINS IN AN AREA NOT
FAVORABLE FOR FURTHER DEVELOPMENT...THE SHEAR IS FORECASTED TO
RELAX OVER THE NEXT DAY OR SO...THUS THERE IS A POSSIBILITY OF
TROPICAL CYCLONE.

...TROPICAL WAVES...
E ATLC TROPICAL WAVE IS ALONG 29W S OF 17N MOVING W 10-15 KT.
LOW AMPLITUDE WAVE WITH WEAK SIGNATURE CURVATURE OBSERVED S OF
13N. SCATTERED MODERATE CONVECTION IS WITHIN THE ITCZ WITHIN 90
NM OF THE WAVE AXIS S OF 9N.

SEE SPECIAL FEATURES FOR LOW/TROPICAL WAVE ALONG 42W/43W.

CARIBBEAN TROPICAL WAVE IS ALONG 73W/74W S OF 20N MOVING W 15
KT. WAVE SIGNATURE CURVATURE IS MASKED BY HIGH CLOUDS THAT COVER
MOST OF THE CENTRAL CARIBBEAN. SCATTERED STRONG CONVECTION IS
INLAND AND ALONG THE IMMEDIATE COAST OF COLOMBIA FROM 9N-11N.

SW GULF OF MEXICO TROPICAL WAVE IS ALONG 95W/96W S OF 21N MOVING
W 10-15 KT. WAVE IS BENEATH AN UPPER CYCLONIC FLOW WHICH IS
DRAWING THE LATE EVENING THUNDERSTORMS OVER S MEXICO INTO THE
BAY OF CAMPECHE. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS INLAND AND ALONG THE IMMEDIATE COAST OF MEXICO E OF THE WAVE
AXIS.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 15N16W 8N25W 15N40W 10N52W 10N63W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM
OF LINE FROM 15N40W TO 7N48W AND MOVING OFF AFRICA FROM 6N-17N E
OF 17W. CLUSTERS OF SIMILAR CONVECTION ARE WITHIN 75 NM OF 9N
FROM 17W-21W AND WITHIN 75 NM OF THE AXIS FROM 33W-36W.

...DISCUSSION...
GULF OF MEXICO...
WEAK MID/UPPER LEVEL LOW IS INLAND OVER MEXICO NEAR 18N97W
PULLING UPPER MOISTURE FROM THE CONVECTION OVER S MEXICO AND THE
TROPICAL WAVE INTO THE BAY. THIS IS BRINGING SCATTERED
SHOWERS/THUNDERSTORMS TO THE AREA. REMAINDER OF THE GULF REMAINS
DOMINATED BY A STRONG UPPER HIGH LOCATED OVER CENTRAL LOUISIANA
NEAR 31N93W WITH PREDOMINANTLY EASTERLY UPPER FLOW ACROSS THE
GULF. AT THE SURFACE...A WEAK RIDGE COVERS THE GULF. SCATTERED
SHOWERS/THUNDERSTORMS ARE OVER FLORIDA S OF LAKE OKEECHOBEE AND
THE STRAITS OF FLORIDA BEING GENERATED BY T.S. KATRINA. THE NE
GULF IS COVERED BY HIGH DEBRIS CLOUDS BUT RADAR INDICATES NO
SHOWER ACTIVITY. MOISTURE WILL BE SPREADING OVER THE GULF AS
T.S. KATRINA CONTINUES TO MOVE TOWARD FLORIDA. GIVEN THE
FORECAST TRACK OF KATRINA...MOST OF THE SHOWERS/THUNDERSTORMS
WILL REMAIN OVER THE E GULF FOR THE BEGINNING OF THE WEEKEND.

CARIBBEAN...
SMALL UPPER LOW IN THE E PACIFIC REGION OFF THE COAST OF
NICARAGUA IS GIVING THE SW CARIBBEAN SE UPPER FLOW...OTHERWISE
THE UPPER FLOW IS GENERALLY EASTERLY ACROSS THE REMAINDER OF THE
BASIN. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 11N
BETWEEN COLOMBIA AND COSTA RICA. AN MID/UPPER RIDGE EXTENDS FROM
NEAR T.S. KATRINA SW OVER HISPANIOLA TO PUERTO RICO WITH
DIFFLUENCE GENERATING CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION N OF 15N BETWEEN THE VIRGIN ISLANDS NEAR 64W
AND HAITI NEAR 73W. DEBRIS CIRRUS CLOUDS COVER THE AREA N OF
14N FROM 64W-81W. THE RIDGE CURRENTLY OVER THE GREATER ANTILLES
WILL BROADEN BY THE WEEKEND TO ENCOMPASS THE W HALF OF THE
CARIBBEAN.

ATLANTIC...
THE STRONG UPPER HIGH OVER THE GULF EXTENDS A RIDGE AXIS OFF
COAST NEAR THE GEORGIA/FLORIDA BORDER E ALONG 30N TO NEAR 73W
THEN NE BEYOND BERMUDA. THIS IS GIVING THE FAR W ATLC N OF T.S.
KATRINA E FLOW. AN UPPER LEVEL LOW IS E OF T.S. KATRINA AND S OF
THE RIDGE EXTENDING FROM THE GULF...CENTERED NEAR 26N67W. THIS
LOW IS EMBEDDED IN DRY UPPER AIR...BUT IS DRAWING MOISTURE
SURROUNDING KATRINA EASTWARD TOWARD THE CENTRAL ATLC. THIS IS
AIDING IN THE GENERATION OF SHOWERS WITH STRONG THUNDERSTORMS S
OF A LINE FROM 29N73W TO 26N65W INCLUDING PUERTO RICO AND
HISPANIOLA. A MID/UPPER TROUGH HAS BEEN INDUCED FROM THE RIDGE
OVER THE NW ATLC AND THE UPPER LOW OVER THE NE ATLC EXTENDING
THROUGH 32N27W ALONG 25N45W TO 24N52W. THIS HAS ESSENTIALLY
SQUASHED THE UPPER HIGH THAT DOMINATED THE CENTRAL ATLC 24 HOURS
AGO. THE TROPICS ARE DOMINATE BY THE RIDGE FROM THE N CARIBBEAN
ISLANDS AND THE RIDGE EXTENDING OFF AFRICA ALONG 16N W ACROSS
THE CAPE VERDE ISLANDS TO 38W...THUS GENERATING THE INVERTED
TROUGH EFFECTING THE TROPICAL WAVE ALONG 42W/43W. STRONG
SUBSIDENCE AND VERY DRY UPPER AIR REMAIN OVER THE W TROPICAL
ATLC FROM THE TROPICAL WEAVE NEAR 42W/4W TO NEAR THE LESSER
ANTILLES.
AT THE SURFACE...THE SUBTROPICAL RIDGE REMAINS ACROSS THE ATLC N
OF 20N E OF 65W.

$$
WALLACE





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